Online Information
Servers will be dedicated
Online play is platform specific; no cross-platform play
Online interaction happens when the player has used an Ember by summoning of phantoms via signs they place on the ground with a White Sign Soapstone. You may also encounter unwelcome invasions from hostile players using invasion items and covenant mechanics.
Up to 6 players can interact in the same session and this happens seamlessly during playing the game, each taking on the roles of cooperator and/or hostile invader. The different Covenants and soapstone signs change the ratio of companions to invader. It is possible to have anything from a 3v3 to a 1v5 scenario.
Using the Dried Finger resets the invasion timer and allows a host player to summon a 3rd phantom as well opening themselvs up to a 2nd invading phantom.
Match making will be level-based again as well as take into account the upgrade level of a player's weapon. Please see the Summon Range Calculator for details.
+/- 10 Soul Levels
+/- 2 Weapon Upgrade Levels
Special weapons that only upgrade up to +5 count as 2x for every upgrade level. So a +1 Unique counts as a +2 for matchmaking purposes, and a +5 counts as a +10.
Weapon Upgrade level seems to apply to your highest upgraded weapon even if you do not have the particular weapon equipped.
Password Matching (as seen in Bloodborne Online) is a feature and disregards the aforementioned soul level and weapon upgrade level matchmaking in lieu of a normalizing adjustment to phantom attack power.
In addition to the basic online parameters listed below, Covenants also alter the multiplayer experience for players. Several of the covenants are defense pacts that send players in to defend a specific area from being completed by exploring players, each with their own specific wrinkle.
Phantoms have half their current estus when in a host's world.
Covenant signs cannot be swapped out when trying to connect to someone else's world.
Hosts, friendly phantoms, and hostile phantoms can get an estus use back if another hostile or friendly phantom dies
Phantoms (Ghosts)
Other players will be shown in the game world as phantoms (ghosts). You cannot interact with phantoms, and they cannot interact with you. Use other phantoms as a guide to what may happen next in-game.
Bloodstains
Examine a blood stain left behind in a spot where another player died, and you'll view a replay of that player's death. Like with phantoms, you can use this as a guide to what may happen next.
Messages
The messages you can write in the main menu will be sent to other players. You'll also receive messages written by other players in your world. Messages can be rated. If other players rate your messages, you'll regain a little HP.
Soul Signs
Use a White Sign Soapstone to cast a soul sign, and that sign will be sent to other players' worlds. If you're summoned from the sign, you'll be transported to the summoner's world. Soul signs can be cast by anyone, whether living or undead, but you must have the power of the Lord of Cinder to summon other players.
http://darksouls3.wiki.fextralife.com/Online